[sundarurfriend]

> Pkg.add can now be told to prefer to add already installed versions of packages (those that already have been downloadedd onto your machine)

> set the env var `JULIA_PKG_PRESERVE_TIERED_INSTALLED` to true.

How is this different from setting `Pkg.offline(true)` and then doing the `add`? I don't know the intricacies of how it works, but that's what I've been doing when I just need to try something out in a temp environment.

[kristofferc]

One difference is that Pkg.offline(true) will error if it cannot resolve something with packages already installed while with this option it will fall back to downloading new versions.